WHen draining it over flows the exist pipe.

The drain pipe in the house may not have a local vent pipe to relieve sewer air pressure or the pipe diameter needs to be increased. I have found that if the hose end is tied into the house drain instead of just sticking it into the pipe end, (sort of like the loose fire-hose nozzle that flips back and forth) that the drain will accept the flood of water. Try that before calling your friendly plumber.

The machine's pump doesn't produce a lot of pressure but it does produce more volume than a faucet. I suspect your drain needs cleaning.